Our present invention relates to a smoothing apparatus and, more particularly, to an apparatus for the smoothing of foils and plates generally of plastic and having a smoothing roll and a smoothing roll drive.
A smoothing apparatus for smoothing of foils and plates of plastic can have a smoothing roll and a smoothing roll drive. Such an apparatus may be used in the production of plastic foils or plastic webs and plastic plates, for example in the context of deep drawing units designed to shape foils or plates. They usually have a plurality of smoothing rolls, for example three smoothing rolls, located one after the other and which serve by contact with the surface of the plastic to remove irregularities therefrom. In the past, such smoothing rolls have been driven by electric motors through appropriate transmissions. However, with the prior art apparatus it was practically impossible to avoid marking of the foil by so-called chatter marks. The problem was most pronounced in the case of thicker foils and plates.
It is, therefore, the principal object of the present invention to provide a smoothing apparatus or device which is capable of producing products of higher surface quality than heretofore and, especially, which is capable of avoiding damage to the product surface or marking.
Another object of the invention is to provide an apparatus which can smooth foil or plate products of plastic without forming chatter marks thereon.
These objects and others which will become apparent hereinafter are attained, in accordance with the invention, in an apparatus for smoothing plastic foils and plates which comprises a smoothing roll and a smoothing roll drive. According to the invention, the smoothing roll drive includes a drive motor having a drive housing, a stator and a rotor, the stator and rotor each being cylindrical and being disposed coaxially with one another in the housing. The rotor is connected directly to a drive shaft of the roll without an intervening transmission.
When we refer to a stator and rotor which are coaxial with one another we mean to indicate that the stator and rotor have a common axis or axes which are located sufficiently close to one another that the stator and rotor can be deemed to be substantially coaxial. The stator and rotor thus have substantially parallel cylindrical outer surfaces and, advantageously, the cylindrical stator surrounds the cylindrical rotor. In other words the rotor is substantially centered in the space surrounded by the stator and both are annular.
The stator can have water-cooling passages according to the invention.
The drive motor of the invention is in the form of an electric motor capable of producing high torque at relatively low speed. Since the rotor is directly coupled to the roll, the rotor speed can correspond to the roll speed of the smoothing roll.
According to a feature of the invention, the rotor surrounds at least part of a connecting sleeve and is preferably fixed on this connecting sleeve. The drive shaft of the smoothing roll can then be fixed to the connecting sleeve. Advantageously the rotor surrounds a cylindrical part of the connecting sleeve which is preferably formed as a hollow cylinder. The rotor can then be fixed to this cylindrical part or hollow cylinder.
According to another feature of the invention, the drive shaft is connected directly with the connecting sleeve and the connecting sleeve can then form simultaneously an extension of the drive shaft. In a highly preferred embodiment of the invention, the drive shaft of the smoothing roll engages in a recess of the connecting sleeve which is opened at the smoothing roll side of the apparatus, this recess also being referred to as a socket herein.
Preferably, in this case, a connecting end of the drive shaft will engage in the recess of the connecting sleeve open at the smoothing roll side and which recess is itself of cylindrical configuration.
The connecting sleeve and rotor can form an assembly which can be journaled on an outer stationary housing part by a bearing, for example a ball or other roller bearing. The outer fixed housing part can also surround the stator and the rotor within the stator. This housing part is preferably of cylindrical configuration. In this embodiment, the connecting sleeve is supported on an outer housing part.
According to a further feature of the invention, on a back side of the drive housing, i.e. a side opposite that at which the roll is located, a back wall is provided which can be connected with the outer stationary housing part and can be used to mount an encoder for measuring the speed of the motor. The back wall is then fixed to the outer housing part which is likewise fixed and the encoder can be located centrally in the back wall and preferably fixed thereto by screws.
In another embodiment of the invention, the assembly of the connecting sleeve and rotor is supported upon an inner stationary housing part by one or more roller bearings. Advantageously this inner housing part is cylindrical and is received in the cylindrical space within the connecting sleeve. In this embodiment the encoder is affixed at a portion of the housing on the roll side, namely, on the inner housing part. Here again the encoder may be centrally mounted on the inner housing part.
The drive shaft of the smoothing roll can likewise be supported in a bearing on a support member, preferably adjacent the connection of the rotor therewith. In this manner an especially reliable support and stabilization of the drive shaft of the smoothing roll is obtainable.
With the apparatus of the invention, smoothing of foils and plates can be carried out to yield products with optimum quality. Surprisingly there are no detrimental chatter marks with the apparatus as compared with prior art systems. The transmission, i.e. gearing, between the electric motor and the roll which has hitherto been required is eliminated and there are thus fewer parts to wear or subject to stress and the need for transmission oil is eliminated. There is thus a reduction in the number of potential places for problems to arise. Maintenance is likewise reduced and the system of the invention provides a vibration-free and low noise operation utilizing an apparatus which occupies considerably less space and is more compact than earlier systems.